Table 2.

Uptake of various organic ions in the HEK293 cells that expressed hMATE2-K at extracellular pH 8.4a

CompoundsVectorhMATE2-K
Uptake (μl/mg protein per 15 min)
    [14C]TEA0.48 ± 0.002.65 ± 0.04b
    [3H]MPP2.44 ± 0.615.56 ± 0.12c
    [3H]cimetidine1.19 ± 0.052.08 ± 0.06b
    [14C]metformin0.85 ± 0.052.48 ± 0.08b
    [14C]creatinine2.60 ± 0.052.68 ± 0.11
    [14C]guanidine11.0 ± 0.028.93 ± 0.21c
    [14C]procainamide12.1 ± 0.9812.0 ± 0.21
    [14C]choline105 ± 0.6991.5 ± 0.18b
    [3H]quinidine137 ± 2.56148 ± 6.16
    [3H]quinine170 ± 7.83229 ± 3.99b
    [3H]thiamine13.8 ± 0.4611.5 ± 0.52c
    [3H]carnitine10.9 ± 0.6710.3 ± 0.70
    [14C]nicotine8.16 ± 0.919.94 ± 0.18
    [14C]captopril0.45 ± 0.020.63 ± 0.05c
    [3H]verapamil11.6 ± 0.2316.0 ± 3.58
    [14C]levofloxacin7.60 ± 1.476.66 ± 0.17
    [3H]tetracycline5.86 ± 0.166.14 ± 0.01
    [14C]p-aminohippuric acid4.90 ± 0.164.54 ± 0.13
    [3H]glycylsarcosine0.70 ± 0.070.59 ± 0.07
Uptake (μl/mg protein per 10 min)
    NMN0.47 ± 0.041.63 ± 0.65c
    cephalexin0.13 ± 0.020.14 ± 0.05
    cefazolin0.17 ± 0.030.10 ± 0.02
    cephradine0.20 ± 0.030.20 ± 0.02
  • a HEK293 cells cultured in a 24-well plate were transfected with the empty vector or hMATE2-K cDNA and incubated for 15 min with incubation medium at pH 8.4 that contained the 19 radiolabeled compounds indicated. After incubation, the radioactivities of solubilized cells were determined. HEK293 cells cultured in a 12-well plate and expressed hMATE2-K were incubated for 10 min with incubation medium at pH 8.4 that contained 1 mM unlabeled N1-methylnicotinamide (NMN) or β -lactam antibiotics such as cephalexin, cefazolin, and cephradine. After incubation, the amounts of each compound extracted from cells were determined by HPLC. Uptake was expressed as clearance, which was obtained from the net uptake value divided by each substrate concentration in the medium. Data represent the mean ± SEM for three monolayers. MPP, 1-methyl-4-phenylpyridinium acetate; TEA, tetraethylammonium.

  • b P < 0.01,

  • c P < 0.05 significantly different from vector-transfected cells.